Question

Consider the following C statements:
char *str1 = "Hello; /* Statement S1 */
char *str2 = "Hello;"; /* Statement S2 */
int *str3 = "Hello"; /* Statement S3 */
Which of the following options is/are correct?

• A. S1 and S2 have syntactic errors
• B. S2 has a lexical error and S3 has a syntactic error
• C. S1 has a lexical error and S3 has a semantic error
• D. S1 has a syntactic error and S3 has a semantic error

Hint:

Check where each error is detected: an unclosed quote is caught by the lexer (lexical error), while assigning a char* string literal to an int* variable is caught by type checking (semantic error).

Answer 1

The Correct Option is C

Look at what each phase of compilation would catch in these three declarations.

In S1, char *str1 = 'Hello;, the quote that starts the string is never matched by a closing quote before the source line ends. The scanner cannot form a valid STRING token, so this is caught at the lexical analysis stage, a lexical error.

In S2, char *str2 = 'Hello;';, the quotes are balanced: the string constant is 'Hello;', containing the characters H-e-l-l-o-; as its value, followed by the actual statement-terminating semicolon. Both the scanner and the parser accept this line without complaint.

In S3, int *str3 = 'Hello';, tokenization and parsing both succeed since 'Hello' is a well-formed literal. The problem only surfaces when the compiler checks types: a string literal decays to char *, but it is being stored in an int * variable. Pointer types disagree, so this is flagged during semantic analysis, not during scanning or parsing.

Thus S1 fails lexical analysis and S3 fails semantic analysis, matching option C.